Holding unit, processing apparatus and holding method of substrates

ABSTRACT

A holding unit for holding a substrate to enable a surface of the substrate to be processed. The unit comprises a vacuum suction member that comes into contact with a peripheral portion of the surface of the substrate and sucks the substrate. A processing apparatus holds the wafer stably and allows an edge, a bevel portion and/or a back surface of the wafer to be processed.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a holding unit, a processingapparatus and a holding method of a substrate, and more particularly toa holding unit, a processing apparatus and a holding method forprocessing a substrate such as a semiconductor wafer that requires ahigh degree of flatness and cleanliness.

[0002] Although aluminum or an aluminum alloy has been commonly used asa material for forming a wiring circuit on a semiconductor substrate,there has arisen a demand in association with the improved density inintegration of semiconductor devices that a material having higherconductivity should be used as the wiring material. To meet that demand,a method has been suggested, in which firstly a plating treatment isapplied to a surface of a semiconductor substrate on which a circuitpattern groove and/or hole has been formed, so as to fill said patterngroove and/or hole with Cu (copper) or Cu-alloy, and secondarily said Cuor Cu-alloy is removed from the surface excluding said portions filledwith it, thus forming a circuit wiring.

[0003] To form this circuit wiring, firstly a conductive layer is formedon the surface of the semiconductor substrate with a semiconductorelement formed thereon, secondarily an insulating film made of SiO₂ isdeposited on the conductive layer, thirdly contact holes and grooves forwiring are formed thereon by the use of lithography etching technology,fourthly a barrier layer made of TiN or the like is formed thereon, andfinally a seeding layer is formed on said barrier layer so as tofunction as a feeding layer for the electrolytic plating.

[0004] By further applying Cu-plating to the top surface of thesemiconductor substrate, the contact holes and/or the grooves of thesemiconductor substrate can be filled with Cu while the Cu-plating filmlayer is deposited on said insulating film. Then, the Cu-plating filmlayer on the insulating film and the barrier layer are removed bychemical mechanical polishing (CMP), so that the surface of theCu-plating film layer filling the contact holes and the grooves forwiring can be approximately flush with the surface of the insulatingfilm. Thereby, the wiring configuration consisting of a copper platingfilm layer is formed.

[0005] In this regard, it is to be noted that since the barrier layerand the seeding layer have been formed respectively to cover almost theentire surfaces of the insulating film or the barrier layer, there is apossibility that the copper film of the seeding layer will exist on abevel (a circumferential portion) of the semiconductor substrate and/orthat the copper forms a film and remains on an inner edge of the bevel(the circumferential portion) of the semiconductor substrate.

[0006] In practice, copper must be completely removed from the substrateotherwise, there is a possibility that any copper that does remain, incertain semiconductor manufacturing process such as an annealingprocess, for example, will readily diffuse into the insulating film,which may cause a deterioration in its insulating ability, orinsufficient adhesion to a film to be formed subsequently, resulting inflaking.

SUMMARY OF THE INVENTION

[0007] In view of these problems, it is an object of the presentinvention, to provide a holding unit, a processing apparatus and aholding method for a substrate, which facilitates processing on an edgeor bevel portion and/or a back surface of the substrate such as a waferand ensures that the substrate is held stably.

[0008] The present invention has been made with this object in mind anand an aspect thereof is characterized by, for example, as shown in FIG.4, a holding unit for holding a substrate W to enable processing of asurface of the substrate W, comprising a vacuum suction member 48 to bebrought into contact with an edge of one of the surfaces of thesubstrate W and to suck the substrate W. Thereby, the substrate can beheld stably with the other surface, a side end portion of the substrateand the peripheral bevel portion on the one surface being exposed, sothat a single process is sufficient to apply surface processing to asubstrate in those respective locations at once.

[0009] Herein, said vacuum suction member has a shape specified suchthat processing is not applied to any portion of the substrate to whichprocessing should not be applied. For example, in the case that thesubstrate is a wafer having an element formed thereon (in a centralportion excluding the edge portion thereof), preferably the vacuumsuction member 48 should be formed so as to define a sucking positionwith respect to the wafer W such that processing such as etching is notapplied to an element (device) forming section of the wafer W specifiedas the non-processing portion, on the substrate. It is furtherpreferable that the shape of the vacuum suction member 48 be defined soas to allow the edge portion of the wafer to be treated as widely aspossible so far as processing is not applied to the element formedsection.

[0010] Preferably, the vacuum suction member 48 has an annular groove 50open in the side facing to the substrate W. In this case, the vacuumsuction member 48 is typically annular in shape. More preferably, thevacuum suction member 48 and the groove 50 are each formed to be annularin shape.

[0011] Further, the vacuum suction member 48 is preferably attached to aback face of a disc-shaped holder plate 44 to be installed horizontally,whereby, since the part of the flat surface defined within the innerside of the sucked surface of the substrate is covered by the vacuumsuction member 48 and the holder plate 44, surface processing is notapplied to that part on the surface, but only to the outside partthereof or the bevel portion of the sucked surface, the side end portionand the back face of the substrate.

[0012] Preferably, a portion of the vacuum suction member 48 to bebrought into contact with the substrate W should be made of a materialhaving lower hardness as compared with that of the substrate W. This isto prevent any scratches from being created on the substrate surface,and also to ensure air tightness with some degree of tight contact tothe substrate surface. A preferable material should be a resilientmaterial such as natural rubber, synthetic rubber and flexible plastic,including fluorine-contained polymers such as PTFE, PFA, and PCTFE(Daifron: Daikin Co. Ltd.) having chemical resistant property and/orheat-resisting property, Kalrez (Dupont, Dow, elastomers, Co., Inc.),Chemraz (Greene, Tweed. Co. Inc.), and Viton (Dupont, Dow, elastomers,Co., Inc.).

[0013] Another configuration of the present invention is characterizedby a processing apparatus of a substrate comprising the holding unitdescribed above and a surface processing unit for applying processing toa surface of the substrate held by said holding unit. In addition, saidprocessing apparatus of the substrate may further comprise a gas-liquidseparation tank 56 which is connected to an exhaust path 52 for creatinga vacuum in the vacuum suction member 48, and to a conduit 54, andfunctions for separating a mixture of liquid and exhaust gas suckedthrough the vacuum suction member 48 into gas and liquid.

[0014] Preferably, the substrate processing apparatus further comprisesa unit for cleaning and/or drying the substrate. Still further,preferably, the substrate processing apparatus comprises an evaluationunit for checking the condition of the substrate after processing iscomplete, and for determining a resultant condition achieved by theprocessing. The processing apparatus of the substrate may furthercomprise a dipping bath for dipping the substrate held by said holdingunit.

[0015] Another configuration of the present invention is characterizedby a holding method for holding the substrate to apply a processing ontoa surface of the substrate, in which the vacuum suction member isbrought into contact with an edge of one of the surfaces of thesubstrate so as to suck by vacuum and thus to hold the substrate.

[0016] In this specification, the term “edge” is used to refer to aperipheral portion on a surface of a substrate such as a semiconductorwhere no device has been formed, typically a portion in a range withinabout 5 mm from a circumferentially end portion on either of the top orthe back surfaces of the substrate. Further, the term “bevel” designatesa portion in a range of typically 0.5 mm or less from a side faceportion or the circumferentially end portion of the substrate, having acurved shape in sectional view or having been chamfered. In addition, aregion covering the edge plus bevel is also referred to as acircumferential portion. Any copper forming a film or adhering to thecircumferential portion must be completely removed immediately after thecopper-film forming process and/or the CMP process to avoid crosscontamination in subsequent processes for conveying, storing andprocessing of the semiconductor substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017]FIG. 1 is a plan view, illustrating a general configuration of anetching apparatus of a first embodiment according to the presentinvention.

[0018]FIG. 2 is a schematic cross sectional front elevation view of theetching unit included in the etching apparatus of FIG. 1.

[0019]FIG. 3 shows a process for delivering a wafer.

[0020]FIG. 4 is a partially cutaway view illustrating a part of a vacuumsuction member for holding a wafer according to a first embodiment.

[0021]FIG. 5 is a partially cutaway view illustrating a part of a vacuumsuction member for holding a wafer according to a second embodiment.

[0022]FIG. 6 is a schematic cross sectional front elevation view of anetching unit of an embodiment according to the present invention.

[0023]FIG. 7 is a flow diagram illustrating a liquid supply system forsupplying DHF or hydrochloric acid.

[0024]FIG. 8 is a flow diagram illustrating a liquid supply system forsupplying A.C.N.

[0025]FIG. 9 is a flow diagram illustrating lines around the etchingunit.

[0026]FIG. 10 is a plan view, illustrating a general configuration of anetching apparatus of another embodiment according to the presentinvention.

DETAILED DESCRIPTION OF THE INVENTION

[0027] Preferred embodiments of the present invention will now bedescribed with reference to the attached drawings. FIG. 1 is anarrangement plan illustrating an overall configuration of an etchingapparatus of an embodiment according to the present invention, and thisapparatus is used for etching a peripheral portion of a device formedregion on a wafer surface, i.e., a circumferential portion thereof (abevel portion and an edge portion), and a back surface of a wafer after,for example, the CVD or the deposition such as sputtering or plating andbefore the wafer being passed to the next process. One of the objects ofthis etching process is to remove any excessive film adhering to theback surface, bevel or notch portion during deposition.

[0028] This apparatus comprises cassettes 10 a and 10 b disposed in oneend side thereof for receiving wafers, and one end functions as a baseend, from which a traveling space 14 for a conveying robot 12 extendstoward the other end. A drying unit 16, a cleaning unit 18, and anetching unit 20 are sequentially arranged in one side of the travelingspace, and an inspection unit 22 is arranged in the other side of thetraveling space 14. Preferably, the conveying robot 12 has at least twohands for handling a dry wafer and a wet wafer separately.

[0029] With reference to a schematic cross-sectional front elevationview of FIG. 2, the etching unit 20 functioning as a surface processingunit will now be described. This etching unit 20 comprises an etchingbath 24 serving as a dipping bath or a surface processing section, awafer holder 26 for holding a wafer W and their associated systems.

[0030] For the sake of convenience, in FIG. 2 as well as FIGS. 3 and 4,which will be referred to later, a vacuum suction member 48 is depictedin a larger scale relative to a substrate W or other components. Inactual scaling, a width of the vacuum suction member 48 is in a range of0.5 to 2 mm while a diameter of the substrate is 200 to 300 mm; and inone embodiment, the width of the vacuum suction member 48 is about 0.75mm.

[0031] The etching bath 24 is cylindrical vessel having a base andcomprises a heater 28 disposed in a specific location, for example, in abottom portion for maintaining a constant temperature in the bath and anetchant supply line 32 extending from an etchant reservoir tank 34 tothe central region of the bottom portion of the bath 24 for supplyingthe etchant 30 into the bath 24 from said central region of the bottomthereof.

[0032] The etchant supply line 32 is provided with a pump 38 for pumpingthe etchant 30 into the etching bath 24, a concentration meter 51(typically, a conductivity meter for liquid taking advantage of the factthat there is a correlation between the conductivity and theconcentration in order to measure the concentration), an inline heater36 for heating the etchant 30 or retaining the heat of the etchant 30,and a chemical filter 53. It is to be noted that neither the heater 28nor the inline heater 36 need necessarily installed at the same time,and each may be mounted as desired. Further, the heaters may beconnected to a thermal sensor and a temperature control unit, though notillustrated, to control the temperature of the etchant 30. In addition,a three-way valve 55 is installed in the line 32 between the chemicalfilter 53 and the bath 24. A third port of the three-way valve 55 to bein communication with other than the line 32 is coupled with a by-passline 39, which is connected to the etchant reservoir tank 34.

[0033] A gutter 40 is arranged in an upper portion of the etching bath24 for receiving any overflowed etchant 30, which is further providedwith a recovery line 42 for guiding the overflowed etchant 30 into aspecified receiver tank.

[0034] Further, the etching unit 20 comprises a transfer mechanism,though not shown, for moving either one of the wafer holder 26 servingas said holding unit and the bath 24 forth or back toward the other.

[0035] The wafer holder 26 comprises a holder plate 44 of horizontaldisc-like shape and a cylinder portion 46 mounted thereon, which areallowed to rotate within a horizontal plane and also to move up and downby a driving mechanism which is not shown. An annular vacuum suctionmember 48 is attached to a lower face of the holder plate 44 along thecircumferential portion thereof as shown in FIG. 3. The annular vacuumsuction member 48 is made of resilient material such as natural rubber,synthetic rubber or a flexible plastic, as described above. A shape,size and material of the vacuum suction member 48 are designed, as willbe described in detail later, so as to ensure that upon being compressedin the opening side of the groove against the substrate W to establish apredetermined degree of vacuum pressure within the groove, it issufficiently to resist excessive deformation, while providing goodsealing to the substrate W, and thus to hold the substrate W stably.

[0036] The concentration meter 51 is used for monitoring a concentrationof the etchant 30 to maintain the constant level of the concentration.The concentration can be controlled by supplying a liquid of highconcentration or a deionized water from a supply port, though not shown.The chemical filter 53 is used for filtering foreign substances such asproducts generated during processing of the substrate. The three-wayvalve 55 is used to switch the etchant supply line 32 from the linecommunicating with the etching bath 24 to the by-pass line 39 when noetching is undergoing. This switching allows the etchant to circulatefrom the reservoir tank 34 passing through the concentration meter 51,the heater 36 and the chemical filter 53 to the reservoir tank 34 again.This circulation helps maintain the temperature, concentration andcleanliness of the etchant in a condition suitable for use in theetching bath 34. It is to be noted that when a filter 53 is arrangeddownstream from the heater 36, it is able to filter any dust that may begenerated in the heater 36.

[0037] A configuration of the vacuum suction member 48 will now bedescribed with reference to a partially sectional view of FIG. 4. Agroove 50 is formed in the vacuum suction member 48, which is aninverted V shape open in the lower side along the centerline thereof.The groove 50 is configured by two ring-shaped members 48 a and 48 beach forming a wall section of the inverted V shaped grooverespectively. The vacuum suction member 48 has at least two ring-shapedmembers 48 a and 48 b to form at least one groove 50 of annular shape(typically annular shape). It is to be noted that three or morering-shaped members 48 a and 48 b may be employed in order to form twoor more grooves 50.

[0038] Now, again referring to FIG. 2, the explanation will becontinued. An exhaust path 52 open to that groove 50 is formed in thevacuum suction member 48 and the holder plate 44, which is incommunication with a gas-liquid separation tank 56 or a scrubber via arotary coupling arranged in the cylindrical portion 46, though notshown, and a conduit 54, and further connected through them to a vacuumsource “Vac” such as a vacuum pump. A vacuum sensor 58 is installed inthe exhaust path or the like to detect a pressure within the groove 50and thereby determine whether the wafer W has been properly held. It isto be noted that for better understanding of the exhaust path 52, whichwill be described later in more detail, the vacuum suction member 48,the holder plate 44 and the cylindrical portion 46 are all illustratedas partially cut away views.

[0039] The relationship between the vacuum suction member 48 and thewafer W will now be described more in detail with reference to FIG. 4.The wafer W has been formed in a disc-like shape comprising a topsurface and a back surface (respective surfaces may be genericallyreferred to as “surface” if appropriate) and a circumferential surface“C”. The circumferential surface C consists of a cylindrical surfacevertical to the top and the back surfaces and (a) chamfered section(s)or (a) bevel(s) “B” connecting said cylindrical surface to the top orthe back surface. Alternatively, the circumferential surface C may beentirely formed in a circular arc shape in sectional view. For either ofthe shapes, a part of the circumferential surface C having a largestdiameter is referred to as an (circumferentially) end portion.

[0040] A region on the top and the back surfaces of the substrate in arange from the end portion to about 5 mm inward from said end portion(with no device formed) is defined as an edge. Herein, for a disc-likewafer W, designating a diameter of the (circumferentially) end portionas “D”, an inner diameter of the circularly annular vacuum suctionmember 48 (an inner diameter of the ring-shaped member 48 b) as “d1”, aninner diameter of the circularly annular groove 50 (an outer diameter ofthe ring-shaped member 48 b) as “d2” and an outer diameter of thecircularly annular vacuum suction member 48 (an outer diameter of thering-shaped member 48 a) as “d3”, a preferable relationship among thesediameters will be the same as that of the case shown in FIG. 5, whichwill be described in further detail later with reference to FIG. 5.

[0041] It is preferable that the vacuum suction member 48 be designed tohave a shape and size which will facilitate processing, such as theetching, without affecting an element (device) forming region on thesubstrate W. In addition, more preferably, the shape and size should bedetermined such that the edge portion can be processed as to as great anextent as possible, so long as processing does not affect the elementformed region.

[0042] The vacuum suction member 48, the holder plate 44 and the wafer Wdefine a space surrounded by those components. That is, the vacuumsuction member 48 is in contact with the wafer W in the vicinity of thecircumference thereof but has no contact with the wafer W in the otherregions, so the space defined by the vacuum suction member 48 togetherwith the holder plate 44 and the wafer W can be a hollow section.

[0043] The wafer to be processed has a specified standard size of, forexample, 200 mm, 300 mm and so on, and also an associatively determineddiameter D of the end portion. Accordingly, when a wafer has beenselected, a corresponding inner diameter dl of the vacuum suction member48 can be determined accordingly.

[0044] An etching process by the etching unit 20 constructed asdescribed above will now be explained below with reference to FIG. 1 andothers. After being subjected to the film forming process such as CVD,sputtering or plating, the wafers W are loaded on the cassette 10 a or10 b with their device formed surfaces up,. They are then each thenremoved by a hand of the conveying robot 12, which is used to carry adry wafer to the etching unit as the robot 12 travels. At this time, thewafer holder 26 is in its lifted position, and the robot hand 60 movesforward thus to transfer the loaded wafer W to a location under thewafer holder 26, and positions the wafer W to be concentric with theholder 26, as shown in the partially sectional view of FIG. 3.

[0045] Then, the wafer holder 26 is moved down, and when the tip portionof the vacuum suction member 48 comes into contact with the wafer W, thevalve 62 (FIG. 2) communicative with the vacuum source Vac is opened togenerate a negative pressure in the space within the groove 50, wherebythe wafer W is sucked and held by the wafer holder 26, as shown in FIG.4. The vacuum sensor 58 installed in the exhaust path 52 or the likedetects the pressure inside the groove 50 and determines that the waferW has been held, and then the wafer holder 26 is moved up and the robothand 60 is retracted. It is to be noted that a temporary loading table,which is not shown, may be provided within the unit; in which case thewafer W can be transferred via that table.

[0046] The wafer holder 26 that has caught the wafer 26 is lowered againso as to dip the wafer W and at least a part of the vacuum suctionmember 48 into a bath liquid 64 in the etching bath 24, as shown in FIG.2. The bath liquid 64 is constantly supplied with the etchant 30 throughthe etchant supply line 32, while the supplied etchant flows away fromthe peripheral portion of the bath 24, thus achieving a steady liquidflow, though a stationary bath may be employed. In the case of thestationary bath, an amount of the etchant should preferably not be morethan 500 cc for the wafer W having the diameter of 200 or 300 mm. Thebath liquid 64 composed of the etchant 30 is maintained at a certaintemperature by controlling a calorific power of the heater 28 and/or theinline heater 36.

[0047] In the case of forming the steady liquid flow, setting a flowvelocity between the bottom of the bath 24 and the wafer W to apredetermined value or greater may help prevent air bubbles fromsticking on the wafer W. To increase the flow velocity, the distancebetween the bottom of the bath 24 and the wafer W should be reduced.

[0048] In either case, it is also possible to rotate the wafer holder 26to maintain an appropriate liquid flow under the surface of the wafer W.A pre-treatment may be applied to the wafer W, including spraying asurfactant and irradiating a plasma against the surface thereof, beforethe wafer W is dipped into the etchant 30,to improve conformabilitybetween the surface of the wafer W and the etchant 30. Turning the waferholder 26 can increase the relative velocity of the etchant with respectto the wafer W, and thus can prevent the air bubbles from sticking tothe wafer W.

[0049] According to this unit, since the etchant is prohibited fromflowing into the inner region on the upper surface of the wafer Wcovered by the vacuum suction member 48, therefore the device formedsurface can be shielded without being etched. On the other hand, thebevel portion B (see FIG. 4) on the top surface, the end face and theback surface of the wafer can be etched all at once, and the surfacelayer can be removed by an amount corresponding to the length of theprocess time or the like together with those deposits such as fineparticles.

[0050] In this unit, even if the sealing property between the contactsection of the vacuum suction member 48 and the wafer W were managedcarefully, it is difficult to completely prevent the etchant fromleaking through the gap therebetween. The leaked etchant is guidedthrough the exhaust path 52 to the gas-liquid separation tank 56 or thescrubber, which separates it into gas and liquid, thus eliminating theaffection of the leaked etchant to the vacuum source such as the vacuumpump.

[0051] After having finished the etching process, the wafer W isprovided with a necessary post-treatment or rinsed with the deionizedwater, and then the wafer is handled through a procedure inverse to theprior loading procedure to be transferred to the robot hand used for awet wafer, which conveys the wafer to the cleaning unit 18. In thecleaning unit 18, a cleaning method such as, if desired, scrubbing orhigh pressure jet spray of deionized water is employed to clean the topand the back surfaces of the wafer W. In this processing, light-etchingby chemicals may be applied to the wafer W as desired. After havingfinished the cleaning process, the wafer W is further transferred by therobot 12 to the drying unit 16, which uses a spin-drying, a clean airjet or the like to dry the wafer W. After having been dried, the wafer Wis returned to the cassette 10 a or 10 b by the robot hand used for thedry wafer.

[0052] In the course of carrying out the processes described above,after either one of the etching, the cleaning and the drying processes,the wafer W is transferred to the inspection unit 22 to determinewhether or not the predetermined etching treatment has been successfullyachieved. The inspection unit 22 may be such an appropriate unit inpractice that comprises, for example, a CCD camera and a computer forimaging an output from the CCD camera. A result determined as eitherpass or fail is stored in the computer, and the subsequent process inresponse to the result applies a suitable processing to the wafer W. Ifthe result is determined a failure, the preceding processes may beapplied again to the wafer W before returning the wafer W to thecassette 10 a or 10 b, or alternatively such a means may be employedthat the a requirement for the process such as the etching may be sentas feedback for processing a next wafer W.

[0053] Now, referring to the partial cross-sectional view of FIG. 5, aconfiguration of an alternative vacuum suction member 148 different fromthat in FIG. 4 will be described. A groove 150 is formed in the vacuumsuction member 148, which is rectangular shape in sectional view open inthe lower side along the centerline thereof. The groove 150 isconfigured by two ring-shaped members 148 a and 148 b each forming awall section of the groove 150 respectively. Although the vacuum suctionmember 148 may have at least two ring-shaped members 148 a and 148 b inorder to form at least one groove 150 of annular shape (typicallyannular shape), three or more ring-shaped members 148 a and 148 b may beemployed, as is the case in FIG. 4.

[0054] An exhaust path 152 open to that grove 150 is formed in thevacuum suction member 148 and a horizontal disc-like holder plate 144for holding the vacuum suction member 148, which is in communicationwith the gas-liquid separation tank 56 or the scrubber as describedabove, and further connected to the vacuum source “Vac” through them. Anoperation for sucking and holding the wafer W is the same as that of thevacuum suction member 48, and a duplicated explanation will be omitted.

[0055] The vacuum suction member 148 is similar to the vacuum suctionmember 48 in those points that the vacuum suction member 148, the holderplate 144 and the wafer W defines a space surrounded by those componentsand that the vacuum suction member 148 is in contact with the wafer W inthe vicinity of the circumference thereof but has no contact points onthe wafer in the other regions thereof so that the space defined by thevacuum suction member 148 together with the holder 144 and the wafer Wcan be a hollow section. Further, in this embodiment, a nitrogen (N₂)purging aperture is provided in the holder plate 144 so that the regionon the upper face (the top surface) of the wafer W covered by the vacuumsuction member 148, i.e., said hollow section can be purged by blowingN₂ gas thereinto.

[0056] Further referring to FIG. 5, the relationship between the vacuumsuction member 148 and the wafer W will now be described. Theillustrated wafer W has a circumferential face C that is round in shapeas a whole. It should be appreciated that the circumferential face C maybe the one in the preceding description that has been chamfered. Herein,for a disc-like wafer W, a diameter of the (circumferentially) endportion is designated as “D”, an inner diameter of the circularlyannular vacuum suction member 148 (an inner diameter of the ring-shapedmember 148 b) as “d1”, an inner diameter of the circularly annulargroove 150 (an outer diameter of the ring-shaped member 148 b) as “d2”and an outer diameter of the circularly annular vacuum suction member148 (an outer diameter of the ring-shaped member 148 a) as “d3”. In oneembodiment, the vacuum suction member 148 is designed such that(d3−d1)/2=0.75 mm, which means the thickness of the vacuum suctionmember 148 to be 0.75 mm, and (d2-d1)/2=0.25 mm, which means the wallthickness of the ring-shaped member 148 b to be 0.25 mm. The ring-shapedmember 148 a is also made with a thickness of 0.25 mm similarly to thering-shaped member 148 b. Accordingly, a width of the circularly annulargroove 150 may be calculated as 0.75−(0.25+0.25)=0.25.

[0057] Further, for D=200 mm, it was determined d3=194 mm, accordingly(D−d3)/2=3.0 mm. In this case, (D−d2)/2=3.5 mm. With this conditionapplied, when the groove 150 was evacuated to vacuum and the wafer W wasdipped into the etching bath while purging the inside of the vacuumsuction member 148 by blowing N₂ gas thereinto, the outside of thering-shaped member 148 b (the outside of the diameter d2) of the wafer Wwas etched but the contact region with the ring-shaped member 148 andthe region inside thereof remained unetched. This is due to the vacuumin the groove 150, the contact region of the ring-shaped member 148 awith the wafer W allows the outer etchant to pass therethrough, whilethe contact region of the ring-shaped member 148 b with the wafer Wallows the inner N₂ gas to pass therethrough, thus shielding the insidefrom the etchant.

[0058] In other words, according to this embodiment, in the case wherethe annular groove 150 formed as interposed between the outerring-shaped member 148 a and the inner ring-shaped member 148 b isevacuated to vacuum so as to suck the wafer W while the inside region ofthe inner ring-shaped member 148 b is purged with N₂ gas, the outerdiameter of the inner ring-shaped member 148 b (the inner diameter ofthe annular groove 150), d2, should be set to be outer with respect tothe region to which no etching effect is expected (typically, the regionin which the element (circuit) has been formed). On the other hand,since the portion with no circuit formed thereon should be etched to asgreat an extent as possible, the diameter d2 is expected to be as nearas possible to a diameter of a circle defining a boundary between aregion with a circuit formed thereon and another region with no circuit.Specifically, D-d2=3.0˜4.0 mm is recommended, and typically, a dimensionof about 3.5 mm is preferred.

[0059] As described, since the wafer to be processed has a standard sizedetermined as 200 mm, 300 mm and so on, once a certain wafer isdetermined to be an subject, the outer diameter of the inner ring-shapedmember of the vacuum suction member 148, d2, can be determinedcorresponding to the size of the wafer. The width of the annular vacuumsuction member 148 is in a range of 0.5˜2.0 mm, preferably in a range of0.5˜1.0 mm, and more preferably about 0.75 mm. It is to be noted thatalthough the sectional shape of the groove 150 is elongated andrectangular, the groove 150 may be formed in an inversed V shape similarto the groove 50.

[0060] With reference to a schematic cross sectional front elevationview of FIG. 6, a configuration and an operation of an etching unit 200and peripheral devices thereof according to an embodiment of the presentinvention will now be described. The etching unit 200, essentiallycomprises: a wafer stage 201 for receiving and delivering a wafer andfor loading the processed wafer thereon to be cleaned; an etching bath221 serving as a dipping bath for applying the etching process therein;a wafer holder 241 for holding the wafer W subject to the etching andfor moving the wafer W between the wafer stage 201 and the etching bath221; a cup 208 arranged so as to surround nozzles 202 and 203 fordischarging wafer cleaning liquid and the stage 201 for preventing theliquid from splashing away; and a frame (not shown) for accommodatingthose components. The unit 200 is coupled with a liquid supply systemincluding a reservoir tank for chemical liquid such as an etchant C_(s)(not shown in FIG. 6) and a chemical liquid pressure pump (not shown inFIG. 6) so as to supply and/or recover the chemical liquid.

[0061] The wafer holder 241 for holding the subject to be etched, thatis the wafer W in this embodiment, includes a holding face having avacuum suction member 148 for holding the wafer W, a mechanism formoving said holding face horizontally between the stage 201 and theetching bath 221, an elevating mechanism, and a shaft for rotating theholding face and a driving source thereof. In the unit used in theembodiment illustrated in FIG. 6, the wafer holder 241 is allowed totravel horizontally by a drive motor 262 for horizontal movement and aball screw 263 between two points: a stage position forreceiving/delivering the wafer W from/to an external component than theunit, and an etching bath position for applying the etching process.Further, the vertical movement operation is controlled by an aircylinder 261, to position the holding face of the wafer W at either oftwo height levels; where one level is to be identical to that of theposition for receiving/delivering the wafer W on the stage 201 and theother level is to be identical to that of the lifted position duringtravel between the etching bath 221 and the stage 201. In addition, arotary mechanism can be provided around the air cylinder 261 placing itas a center of rotary motion to accomplish the horizontal travel.

[0062] It is to be noted that although in FIG. 6, the etching positionfor applying the etching process is shown at the same height level as ofthe position for receiving/delivering the wafer W, the etching positionmay be determined at a different level. Further, a rotary shaft motor242 enables the holding face to rotate at a rotational speed of 0 to 500revolutions/min. To explain in further detail, the wafer holder 241 forholding the wafer W comprises a horizontal disc-like holder plate 144and a cylindrical rotary shaft 243 mounted thereon in its centralportion. An upper end of the rotary shaft 243 is coupled to the rotaryshaft motor 242 attached to one end of a horizontally extending arm 244,so that the rotary shaft 243 can be rotated by the motor 242. The otherend of the arm 244 is coupled to a piston of the air cylinder 261 sothat the arm 244 can be moved in the up and down directions by thepiston and also in the rotary direction around a piston rod as centered.Further, the annular vacuum suction member 148 is attached to the backsurface of the holder plate 144 along the peripheral edge portionthereof, as has already been described.

[0063] The stage 201 for receiving/delivering the wafer W comprises arotary table 205 having a rotary face arranged horizontally whichincludes a plurality of pins 204 attached thereon for supporting theperipheral edge portion of the loaded wafer W. A rotary shaft 206 isfixed to the under face of the rotary table 205 upright in a centralportion thereof, and the rotary shaft 206 is coupled with a rotary shaftmotor 207 so as to be driven rotationally thereby.

[0064] The rotary table 205 with the pins 204 may function as a relaytable upon receiving/delivering the wafer W between the wafer holder 241and the robot hand 210 and also may function as a table on which thewafer W is loaded upon cleaning the top and the back surfaces of thewafer while allowing the wafer W to be rotated during cleaning. Therotational speed is in a range of 0 to 3000 revolutions/min. It is to benoted that the robot hand 210 is illustrated in FIG. 6 with thedirection of its movement designated by a horizontally bidirectionalarrow. It is to be further noted that although the robot hand 210 isshown as if it were penetrating through the cup 208, in practice, thecup 208 and a shutter, which is not shown, are moved down cooperatively(see a vertical bi-directional arrow 211) to permit the robot hand 210to access a location above the rotary table 205.

[0065] It is to be appreciated that the wafer stage 201 may employconfigurations other than that of the illustrated one having the pinsand the rotary table, and it may comprise, for example, six supportingshafts (not illustrated) each of which is operatively attachedvertically onto the wafer stage so as to be capable of rotating and isconfigured to catch the loaded wafer W in the peripheral portionthereof. The wafer W may be loaded at upper end portions of thosesupporting shafts and allowed to rotate as the supporting shafts rotate.

[0066] The etching bath 221 for applying the etching process has asupply port 222 for supplying the etchant C_(s) and a drainage hole(DRAIN) 223 a in a bottom portion of the bath. Further, a liquid levelsensor 224 is attached to the bath in an upper location thereof so as todetect a full level, i.e., an overflow, of the etchant in the etchingbath 221 and a drainage of the etchant. The etching bath 221 is acylindrical vessel having a base, and an etchant supply line is providedso as to establish a communication between the etchant reservoir tank(not shown in FIG. 6) and the etching bath 221.

[0067] The etching bath 221 is provided with a gutter 225 arranged in aside portion thereof for receiving overflowed etchant, and the gutter225 has a drainage hole (DRAIN) 223 b penetrating therethrough, to whicha recovery line is connected for recovering overflow etchant into theetchant reservoir tank (not shown in FIG. 6). Also, the etchant drainedfrom the drainage hole 223 a in the bottom portion of the etching bathjoins into the same recovery line. It is to be noted that the etchantsupply line may also be used as a flow path for supplying the deionizedwater W_(a) into the etching bath 221.

[0068] A thermo-couple 226 is attached to the etching bath 221 formeasuring a liquid temperature within the bath so as to see whether ornot the etchant has reached to a temperature suitable for processing.

[0069] The cup 208 surrounding the stage 201 is provided with twonozzles: one is a nozzle 202 for cleaning a top-surface of the wafer andthe other is a nozzle 203 for cleaning a side-face of the wafer. Also,the stage 201 in its central portion is provided with another nozzle 209for cleaning a back surface of the wafer, serving as a discharge portdirected upward so as to inject a cleaning liquid to be used forcleaning the back surface of the wafer W. Although in the aboveembodiment deionized water is used as the cleaning water, the nozzlesmay be connected to other chemical lines. It is to be noted that the cup208 is disposed in an outer periphery with respect to the stage 201supporting the wafer W, and during the wafer W being processed, the cup208 is lifted up so as to cover the stage 201, thus preventing cleaningliquid from splashing away over the cup 208. The lifting and loweringmotion of the cup 208 is controlled by an air cylinder, though notshown.

[0070] It is to be noted that the non-illustrated shutter is attached tothe cup 208 and moves up or down in association with the lifting andlowering motion of the cup. This shutter is in contact with a side faceof a not-illustrated frame, and has a geometric relationship.

[0071] The frame for accommodating the unit can receive and support allof the aforementioned mechanisms and a side face of the frame has anopening for carrying/taking the wafer in/out of the frame. The shutteris in contact with an inner side of the side face portion of the framehaving the carrying in/taking out opening, and in operation, the openingremains open when the cup 208 has been lowered but would be blocked bythe shutter sliding up when the cup has been lifted up.

[0072] The unit of FIG. 6 operates generally in the following manner.Firstly, the wafer W to be etched is set on the stage 201. Then, thewafer holder 241 sucks and thus holds the wafer W with the vacuumsuction member 148, and transfers the wafer W to the etching bath 221,in which the wafer W is etched while being held by the wafer holder 241.Then, after a rough cleaning (a rinse) having been applied to the waferW within the etching bath 221, the wafer W is transferred onto the stage201, in which a main cleaning operation is carried out with thedeionized water being applied to the wafer W to finish the process, andthe wafer W is now ready to be taken to the outside.

[0073] In conjunction, operations of the peripheral devices and thecomponents during said operation will be described below in detail.Firstly, the wafer W subject to etching, as in the state of being loadedon the robot hand 210, is carried by the robot to the main etching unit200. At that point in time, the wafer holder 241 is in a standby stateat the lifted position above the etching bath 221.

[0074] The robot hand 210 is introduced into the etching unit 200 alongthe level of the upper face of the stage 201 through the opening forcarrying in/taking out the wafer arranged in the side face of the frame.The robot hand 210, after having reached to the location right above thestage 201, is lowered to place the wafer W on the stage 201. The robothand 210 having been lowered to a level lower than the wafer W isretracted through said opening.

[0075] When the retraction of the robot hand has been completed, thewafer holder 241 is moved horizontally to the location above the stage201 and then the wafer holder 241 is lowered to the level of the stage201. At that time, the wafer holder 241 comes in contact with theperipheral edge portion of the wafer W at the vacuum suction member 148,which is a sealing of the holding section of the wafer holder 241, andsucks the wafer W by vacuum. Preferably, the pressure at this timeshould be in a range of not greater than −80 kPa.

[0076] After that, the space formed by the vacuum suction member 148 andthe top surface of the wafer W is supplied with N₂ gas to increasepressure within the space, while the exhaust gas E_(g) is dischargedfrom the upper peripheral portion of the etching bath 221, so that theetchant may be prohibited from wrapping around and entering into theinterior space. This N₂ gas hardly increases the pressure compared withthe ambient. By supplying the N₂ gas in such a manner, the vacuumsuction pressure of the sealing section comes into a range of −60 kPa orlower. Under this condition, the wafer holder 241 is moved up by the aircylinder 261 and further moved in the horizontal direction to thelocation above the etching bath 221, where the wafer holder 241 islowered to the etching position.

[0077] Subsequently, the etching bath 221 is supplied with the etchantC_(s), the temperature of the etchant is detected by the thermo-couple226 to see that the detected temperature is at a predetermined level,and it is ensured by using the liquid level sensor 224 that the bath hasbeen filled with a sufficient amount of etchant. After this has beenensured, the etching process is applied for a certain period of timewhile rotating the holding face of the wafer holder 241 at a rotationalspeed of about 0 to 50 revolutions/min. and also supplying the etchant.It is to be noted that the etching time may be determined arbitrarily.

[0078] In the case where the film on the wafer to be etched was Ta₂O₅film of 200 angstrom thick, a good etching result was obtained with theetchant of DHF by 5%, the etchant temperature of 50° C. to 80° C., andthe etching time of one minute. Further, rotating the holding face ofthe wafer holder 241 during etching can prevent the air bubblesgenerated by the etching reaction from being retained on the wafer W,and thus is able to prevent uneven etching. In addition, the continuoussupply of the etchant C_(s) during etching is also effective. Forexample, supplying the etchant at a flow rate of 800 to 1000 cc/min hasbeen found effective.

[0079] When the predetermined etching time has passed, the etchant isdischarged and the same etching bath is now supplied with the deionizedwater W_(a) to roughly clean the wafer W and the portion around thesealing section of the wafer holder 241. This rough cleaning time mayalso be determined arbitrarily. When the rough cleaning has beencompleted, the rinse liquid in the etching bath 221 is discharged, andthe wafer holder is lifted up and then moved to the location above thestage 201. At this point of time, the cup 208 is moved up, and thedeionized water is injected from the cleaning liquid supply nozzle 203for the wafer side-face against the back surface and edge portion of thewafer W so as to practice the cleaning. Then, the wafer holder 241 islowered to the level of the stage 201 to release the suction. At thistime, the release of the wafer W and the cleaning of the interior of thesealing can be performed at the same time by supplying the deionizedwater (D.I.W.) to the vacuum line, which has been used to suck the waferW, in a direction toward the wafer holding surface.

[0080] After the wafer W has been loaded on the stage 201, the top andthe back surfaces of the wafer are cleaned by injecting deionized waterfrom the nozzle 202 to thereby clean the wafer top-surface (upper face)and the central discharge port 209 of the stage 201.

[0081] When all of the processes including etching prior to cleaninghave been completed in the manner as described above, the robot isdirected toward the unit in order to receive the wafer W. In the etchingunit 200, the cup 208 of the stage is lowered. In this way, as theopening arranged in the side face of the frame for receiving/deliveringthe wafer is opened, the robot hand 210 is inserted at the level lowerthan the wafer and then moved up from this state to scoop the wafer outof the stage, and the hand is contracted to bring the wafer to theoutside.

[0082] The above explanation has been directed to the etching of theTa₂O₅ film but the unit of the present invention can be applied foretching other kinds of films by exchanging the etchant. For example, fora Ru film, a solution of ammonium cerium nitrate by 20% may be suppliedas the etchant. For a TiN film, hydrochloric acid, hydrogen peroxidewater, and deionized water may be mixed by a ratio of, for example,1:1:5 just before supply and then supplied. In either case, the etchantmay be heated to 50° C. to 80° C. and then supplied. Further, althoughin this description N₂ gas is supplied to prevent wraparound andentering of the etchant and vapor, air, or another gas may be used.

[0083] Now referring to flow diagrams of FIGS. 7, 8 and 9, a liquidsupply system, that is, an etchant reservoir tank and its peripheraldevices, for supplying the etchant to the etching unit of the embodimentaccording to the present invention will now be described. The unitaccording to the present invention allows three kinds of etchant to beselectively supplied. A first etchant is dilute hydrofluoric acid (DHF),a second etchant is dilute hydrochloric acid, and a third etchant is asolution of ammonium cerium nitrate. In this group, the dilutehydrofluoric acid (DHF) and the dilute hydrochloric acid are liquid thatis not precipitated, but the ammonium cerium nitrate is a solution to beprecipitated. The reservoir tank system may be constituted differentlydepending on the etching solution being precipitated or notprecipitated.

[0084] With reference to the flow diagram of FIG. 7, a supply system ofthe etchant that is not precipitated or hardly precipitated will beexplained. A liquid pressure pumping line 311 for taking out the etchantfrom an etchant reservoir tank 301 and for returning it to the reservoirtank 301 is arranged with its inlet port coupled to a lower portion ofthe reservoir tank 301. In the pressure pumping line 311, a pump 302 forpressure-pumping the etchant, a heater 303 for heating the etchant, anda flow meter 304 for measuring the flow rate of the etchant flowingthrough the pressure pumping line 311 are respectively installed in thissequence as starting from the side of the reservoir tank 301.

[0085] The pressure pumping line 311 is branched at a downstream side ofthe flow meter 304 into an etchant supply line 312 leading to an etchingbath 24(1) of the etching unit and an etchant circulation line 317leading to the etchant reservoir tank 301. The etchant circulation line317 is provided with a conductivity meter 305 for measuring aconductivity of the etchant circulating without being supplied to theetching bath. The conductivity meter 305 is a measuring instrument foruse in determining a concentration of the etchant by measuring theconductivity. This is based on the fact that there is a correlationbetween the conductivity and the concentration of the etchant. Theetchant circulation line 317 in its return side is connected to an upperportion of the reservoir tank 301.

[0086] Further, a liquid level sensor 307 for monitoring the liquidlevel of the etchant within the reservoir tank 301 is installed in anoutside of the reservoir tank 301.

[0087] Further, a dilute hydrochloric acid make-up line 314 forreplenishing the reservoir tank 301 with the dilute hydrochloric acidand a dilute hydrofluoric acid make-up line 315 for replenishing thereservoir tank 301 with the dilute hydrofluoric acid are connected tothe etchant reservoir tank 301. In addition, a drainage line (DRAIN) 316for discharging the etchant in the etchant reservoir tank 301 isconnected to the bottom portion of the etchant reservoir tank 301.

[0088] An operation of an etchant reservoir tank system equipped withabove components will be described. Firstly, an etchant to be used, forexample, a solution of DHF by 5% is made from a solution of DHF by 50%mixed with deionized water (D.I.W.) and the etchant reservoir tank isfilled with a predetermined amount of the etchant. A filling amount ofthe etchant can be monitored by the liquid level sensor 307. The liquidlevel sensor 307 is designed such that a highest level HH, a higherlevel H, a lower level L and the lowest level LL can be detected. Anacceptable amount is determined as an intermediate level between thelevel H and the level L. When the DHF etchant is used, the valve, whichis not shown, should be closed with respect to the hydrochloric acidmake-up line 314.

[0089] Once the reservoir tank fills with an appropriate amount ofetchant, the pump 302 is actuated to start pressure-pumping of theetchant. The etchant pumped out of the pump 302 is heated by the heater303 to a predetermined temperature required in the etching unit. Theflow meter 304 can measure the flow rate of the etchant flowing throughthe pressure pumping line.

[0090] The etchant heated by the heater is supplied to the etching bath24(1) in the etching unit, which will be explained later in detail,through the supply line 312 to the etching bath 24(1). At that time, aflow rate control valve 306 controls the flow rate of the etchant to alevel required in the etching bath. Further, as will be explained later,any DHF etchant overflow in the etching bath or discharged from thedischarge port can be returned to the bath through the return line 313from an etching bath 24(3). In this way, the DHF etchant may berecovered and reused. Since the etchant is expensive, it is importantfor it to be able to reused. the efficient use of resources.

[0091] While no etchant is supplied to the etching bath, the etchanttemperature is maintained at the constant level by circulating theetchant from the pressure pump 302 through the heater 303, the flowmeter 304, and the conductivity meter 305 to the reservoir tank 301. Itis to be noted that a filter, which is not shown, may be installed inthe pressure pumping line 311, for example, downstream to the heater303. This filter may help remove the etching products or the like in theline. Further, since the water content in the etchant may be vaporizeddue to the circulation of the etchant or the etchant composition may bechanged due to the etching reaction, the unit has been equipped with afunction for managing the etchant by measuring the amount of the etchantusing the liquid level sensor 307 arranged in the reservoir tank 301 andby measuring the concentration of the etchant using the conductivitymeter 305 arranged in the line and thereby to replenish the reservoirtank 301 with the etchant or the deionized water.

[0092] To explain in more detail, the reason why the concentration ofthe etchant can be known by measuring the conductivity of thecirculating etchant using the conductivity meter 305 is that thedecreased conductivity could be determined due to the decreasedconcentration. When the conductivity decreases, the make-up linesupplies new DHF etchant in order to increase the conductivity to thecertain level corresponding to the concentration level required by theetching unit. Upon this adjustment, if the liquid level of the reservoirtank 301 has increased excessively, then the etchant may be dischargedvia the drainage line 316.

[0093] In the event of higher conductivity, contrarily the deionizedwater should be refilled. Although there is a possibility of the watercontent in the etchant being vaporized resulting in a higherconcentration of the etchant becomes higher, the liquid sensor 307monitoring the liquid level can detect this event and the deionizedwater should be accordingly refilled to maintain the predetermined levelof the concentration. That is, the use of the liquid level sensor 307 orthe conductivity meter 305 can help maintain the concentration at anacceptable level. The use of each component in combination enables moreaccurate control of the concentration. These functions make it possibleto reuse the etchant.

[0094] When the etching process has been completed and the used etchantis to be discharged from the reservoir tank 301, the valve installed inthe line 316, though not shown, is opened. Although the same unit may beused for the DHF and also for the hydrochloric acid, if a differentetchant is to be used, the reservoir tank 301 and its associated linesshould be cleaned thoroughly with the deionized water to remove thepreviously used etchant.

[0095] It is to be appreciated, that when this etchant supply system isused for the hydrochloric acid, the etchant should not be returned tothe reservoir tank 301 through the return line 313 but the etchant afterbeing used in the etching bath is recovered into a tank, which is notshown, and the reservoir tank 301 is refilled with new etchant.

[0096] Now referring to the flow diagram of FIG. 8, a liquid supplysystem for the etchant to be precipitated will be explained. A liquidpressure pumping line 331 for taking out the etchant from an etchantreservoir tank 321 and for returning it back to the reservoir tank 321is arranged with its inlet port coupled to a lower portion of thereservoir tank 321. In the pressure pumping line 331, a pump 322 forpressure-pumping the etchant, a heater 323 for heating the etchant, anda filter 328 for filtering the etchant are respectively installed inthis sequence as starting from the side of the reservoir tank 321.

[0097] The pressure pumping line 331 is branched at a downstream side ofthe filter 328 into an etchant supply line 332 leading to an etchingbath (liquid bath) 24(2) of the etching unit and an etchant circulationline 337 leading to the etchant reservoir tank 321. The etchantcirculation line 337 is provided with a flow meter 324 for measuring aflow rate of the etchant flowing through the circulation line 337 and aconductivity meter 325 for measuring a conductivity of the etchantcirculating without being supplied to the etching bath.

[0098] The conductivity meter 325, similar to the conductivity meter305, is a measuring instrument to be used for determining aconcentration of the etchant by measuring conductivity. The etchantcirculation line 337 in its return side is connected to an upper portionof the reservoir tank 321. It is to be appreciated that the flow meter324 may be installed in the pressure pumping line 331 as in the casedescribed with reference to FIG. 7.

[0099] Further, a liquid level sensor 327 for monitoring the liquidlevel of the etchant within the reservoir tank 321 is installed outsidethe reservoir tank 321.

[0100] Further, an A.C.N. make-up line 334 for replenishing thereservoir tank 321 with ammonium cerium nitrate (A.C.N.) is connected tothe etchant reservoir tank 321. In addition, a drainage line (DRAIN) 336for discharging the etchant contained in the etchant reservoir tank 321is connected to the bottom portion of the etchant reservoir tank 321,and the drainage line 336 is connected to a three-way valve 339, oneport of which is connected to the recovery line 337 leading to an A.C.N.recovery tank 340 and the other port of which is connected to a drainageline 338.

[0101] An operation of an etchant reservoir tank system equipped withabove components will be described. Firstly, an etchant to be used,i.e., a solution of A.C.N. by 20% is made from a solution of A.C.N., forexample, by making a mixture containing 50% deionized water (D.I.W.),and the etchant reservoir tank is filled with a predetermined amount ofthe etchant. Filling of the etchant can be monitored by the liquid levelsensor 327. An acceptable amount of the etchant is determined as anintermediate level between the level H and the level L in the scale ofthe liquid level sensor 327.

[0102] When the reservoir tank has been filled with the acceptableamount of the etchant, the pump 332 is actuated to start thepressure-pumping of the etchant. The pumped-up etchant is heated by theheater 323 to a predetermined temperature required in the etching unit.The heated etchant passes through the filter 328, so that the etchingproducts or the like can be removed therefrom.

[0103] The etchant heated by the heater to an appropriate temperature,and further filtered by the filter 328 to be purified is supplied to theetching bath 24(2) through the supply line 332 to the etching bath24(2). At that time, a flow rate control valve 336 controls the flowrate of the etchant. Further, any etchant overflowed in or dischargedfrom the etching bath 24(4) may be returned to the reservoir tankthrough the return line 333. In this way, the etchant can be recoveredand reused.

[0104] At the time that no etchant is being supplied to the etching bath24(2), the etchant temperature is maintained to be maintained constantby circulating the etchant from the pressure pump 322 through the heater323, the filter 328, the flow meter 324, and the conductivity meter 325to the reservoir tank 321. It is true in this case as similar to that ofFIG. 7, that the acceptable concentration level of the etchant can bemaintained by the use of the liquid level sensor 327 and/or theconductivity meter 325.

[0105] The three-way valve 339 is used when the etching has beencompleted and the used etchant is to be discharged out of the reservoirtank 321. When the three-way valve 339 is operated to establish acommunication between the line 336 and the line 338, the etchant isallowed to drain to the outside, while on the other hand when thethree-way valve 339 is operated to establish communication between theline 336 and the line 337, the etchant can be recovered into the A.C.N.recovery tank 340.

[0106] With reference to the flow diagram of FIG. 9, a configuration andoperation of the etching unit to be supplied with the etchant from theetchant supply system described above will now be described. Herein, theetching bath 221, which has been described with reference to FIG. 6, isused as the etching bath.

[0107] A DHF/hydrochloric acid· hydrogen peroxide water line 357, anA.C.N. line 332, a deionized water (D.I.W.) line 358 and a drainage line359 are respectively connected to the etching bath 221. In the line 357,a three-way valve 351 functioning as a mixing valve is installed in alocation just before an inlet port into the etching bath 221. Two of theports of the three-way valve 351 are respectively connected to thesupply line 312, which has been described with reference to FIG. 7, andto the hydrogen peroxide water supply line 356.

[0108] The three-way valve 351 has been designed as such a mixing valvethat can be switched between one case where the line 312 is incommunication with the line 357 with blocking the line 356 and the othercase where both of the line 312 and the line 356 are in communicationwith the line 357. When the line 312 is used to supply the DHF, thethree-way valve 351 is switched to the other case so that the hydrogenperoxide water can be supplied from the line 356 to be mixed with theDHF, and when the line 312 is used to supply the hydrochloric acid, thethree-way valve 351 is switched to the one case to block the line 356.

[0109] The A.C.N. line 332 is a line for supplying the A.C.N. which hasbeen heated and filtered as described with reference to FIG. 8. Thedeionized water (D.I.W.) line 358 is a line for supplying the deionizedwater to clean the etching bath and so on if desired.

[0110] The drainage line 359 is a joint line of the lines from the ports223 a and 223 b described with reference to FIG. 6 and connected to athree-way valve 352. One of the ports of the three-way valve 352 isconnected with the drainage line 360, through which the used acid,alkali and DHF are drained. Another one of the ports of the three-wayvalve 352 is connected to another three-way valve 353. One of the portsof the three-way valve 353 is connected with the return line 313 runningfrom the etching bath 24(3) to the reservoir tank as described withreference to FIG. 7, and another one of the ports is connected with thereturn line 333 running from the etching bath 24(4) to the reservoirtank.

[0111] The tree-way valves 352, 353 can switch lines depending on theliquid to be used. It is to be noted that said two three-way valves maybe replaced with a single four-way valve which can switch the line 359to be in communication with either of the line 313, 333 or 360.

[0112] The relationship between the film to be etched and the etchant inthe etching unit described above may be, for example, as describedbelow.

[0113] For an Ru film, a solution of ammonium cerium nitrate by 20% issupplied as the etchant at a temperature of 80° C. This etchant may beused while circulating.

[0114] For a film of Ta₂O₅, a solution of dilute hydrofluoric acid by50% at 80° C. may be supplied as the etchant. This etchant may be usedwhile circulating.

[0115] For a TiN film, a solution of hydrochloric acid mixed withhydrogen peroxide water by a ratio of 1:1.5 at a temperature of 65° C.to 70° C. is supplied as the etchant. After having been used in theetching bath, this etchant is stored in the etchant reservoir tank to besubjected to a treatment as a drain liquid. The hydrogen peroxide watershould be mixed with the hydrochloric acid just before the etching bath(mixing at a use point).

[0116] As has been described above, according to an etching unit of anembodiment of the present invention, by using a vacuum suction member 48or 148 it is possible to prevent a region on the wafer within the vacuumsuction member from coming into contact with the etchant and inparticular, can shield a circuit section formed on the wafer completelyfrom the etchant.

[0117]FIG. 10 shows a general configuration of an etching apparatus ofanother embodiment, in which a cleaning unit and a drying unit areintegrated to be a single cleaning/drying unit 18A. This may be achievedby, for example, providing a spin-dryer with a deionized water injectingmeans. Thereby, the number of units can be decreased by one and all ofthe units can be arranged surrounding the robot 12, so that a set of theunits has been successfully made compact with the robot 12 of a fixedtype. Further, owing to no more travel of the wafer W between thecleaning unit and the drying unit, the process time can be shortened.

[0118] It is to be noted that although the above explanation has beengiven illustratively to the embodiment where the holding unit of thewafer according to the present invention is applied to the etchingprocess, the application thereof is not limited to this, but thisholding unit may be applied broadly to a variety of surface processingapparatuses including those for cleaning, drying and so on using aprocessing media of liquid or gas. Further, since in this holding unit,a substrate can be held stably by applying a vacuum suction to aperipheral portion of the substrate, this unit may be employed in suchan apparatus that requires a mechanical holding strength for polishingthe wafer W or the like.

[0119] According to the present invention as described above, since aholding unit comprises a vacuum suction member which comes into contactwith an edge of one surface of the substrate and sucks said substrate,it can hold the substrate stably with the other surface of thesubstrate, a circumferential portion of the substrate, and especially aperipheral portion, for example, a bevel portion of said one surfacebeing exposed. Accordingly the surfaces can be processed with theseportions exposed.

[0120] For example, after a film forming process such as CVD, sputteringor plating, if the wafer is held at its top surface and the etchingand/or cleaning is applied to that surface, any undesirable films on theback surface and the circumferential portion, specifically the bevelportion, can be removed at the same time, thus reducing a processingtime, and also ensuring uniform processing at those locations.

What is claimed is:
 1. A holding unit for holding a substrate which hastwo parallel surfaces to process the surfaces, comprising: a vacuumsuction member brought into contact with a peripheral portion of one ofsaid surfaces of said substrate to suck said substrate.
 2. A holdingunit of claim 1, wherein said vacuum suction member is shaped so thatprocessing is applied to only a portion of said substrate to which suchprocessing should be applied.
 3. A holding unit of claim 1, wherein saidvacuum suction member has an annular groove formed therein, and which isopen in the side facing said substrate.
 4. A holding unit of claim 1,wherein a material forming a portion of said vacuum suction member to bebrought into contact with said substrate is a material having a hardnesslower than that of said substrate.
 5. A processing apparatus forprocessing a substrate, comprising: a holding unit of claims 1; and asurface processing unit for processing a surface of the substrate heldby said holding unit.
 6. A processing apparatus of claim 5, furthercomprising a unit for performing at least either one of cleaning ordrying of the substrate.
 7. A processing apparatus of claim 5, furthercomprising a dipping bath for dipping the substrate held by said holdingunit.
 8. A processing apparatus of claim 5, further comprising anevaluation unit for checking a condition of the substrate afterprocessing and for determining a resultant condition achieved by saidsurface processing.
 9. A method for holding a substrate to process asurface of said substrate, said method comprising the steps of: bringinga vacuum suction member into contact with a peripheral portion of one ofthe surfaces of said substrate, and holding said substrate by suckingsaid substrate under a vacuum.